v3.0 Extending API Platform

Extending API Platform

Because it handles the complex, tedious and repetitive task of creating an API infrastructure for you, API Platform lets you focus on what matter the most for the end user: the business logic. To do so, API Platform provides a lot of extension points you can use to hook your own code. Those extensions points are taken into account both by the REST and GraphQL subsystems.

The following tables summarizes which extension point to use depending on what you want to do:

Extension PointUsage
State Providersadapters for custom persistence layers, virtual fields, custom hydration
Denormalizerspost-process objects created from the payload sent in the HTTP request body
Voterscustom authorization logic
Validation constraintscustom validation logic
State Processorscustom business logic and computations to trigger before or after persistence (ex: mail, call to an external API…)
Normalizerscustomize the resource sent to the client (add fields in JSON documents, encode codes, dates…)
Filterscreate filters for collections and automatically document them (OpenAPI, GraphQL, Hydra)
Serializer Context Builderschange the Serialization context (e.g. groups) dynamically
Messenger Handlerscreate 100% custom, RPC, async, service-oriented endpoints (should be used in place of custom controllers because the messenger integration is compatible with both REST and GraphQL, while custom controllers only work with REST)
DTOsuse a specific class to represent the input or output data structure related to an operation
Kernel Eventscustomize the HTTP request or response (REST only, other extension points must be preferred when possible)

Doctrine Specific Extension Points

Extension PointUsage
ExtensionsAccess to the query builder to change the DQL query
FiltersAdd filters documentations (OpenAPI, GraphQL, Hydra) and automatically apply them to the DQL query

Leveraging the Built-in Infrastructure Using Composition

While most API Platform classes are marked as final, built-in services are straightforward to reuse and customize using composition.

For instance, if you want to send a mail after a resource has been persisted, but still want to benefit from the native Doctrine ORM state processor, use the decorator design pattern to wrap the native state processor in your own class sending the mail, as demonstrated in this example.

To replace existing API Platform services with your decorators, check out how to decorate services.

Service Decoration screencast
Watch the Service Decoration screencast

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